Interpretive Summary: The mechanism by which soil acidity reduces the yield of many crops has been studied extensively. However, few studies have been conducted to screen common bean germplasm for acid soil tolerance under field conditions in the tropics. Identification of potential sources of bean germplasm with acid soil tolerance is critical since the most productive soils of the world are already under cultivation, and those available for agricultural expansion are often strongly acid, possessing toxic levels of soil aluminum. A 2-yr field study to screen five bean genotypes for acid soil tolerance demonstrated differences for dry matter production in both dry and snap beans grown under Al stress. However, even among genotypes which presumably have some degree of tolerance to Al, these differences may be of little practical value under the conditions normally encountered in the tropics where the amounts of soil Al cause large reductions in yield. In view of these results, the authors are presently screening 100 bean genotypes in a continued effort to identify Al-tolerant germplasm for this important crop.

Technical Abstract:
Tolerance to soil Al differ greatly among grain legume species. However, there is insufficient information on the response of common bean (Phaseolus vulgaris) to Al stress under field conditions. A 2-yr field study was conducted to determine the effects of various levels of soil Al on dry matter production and mineral concentration in the leaves of five genotypes sof common beans. Increasing the concentration of soil Al caused a significant decline in total, stem, pod and grain dry weights in all genotypes. Increasing soil Al concentration from 0.68 cmol/kg to just 2.5 cmol/kg reduced the total dry weight of all genotypes between 25% and 31%. Increments in soil Al resulted in a significant reduction in leaf P, Ca, and Mg and an increase N, Fe and Al. Leaf K and Zn increased up to a soil Al concentration of about 8 cmol/kg and then declined sharply. The results of this study demonstrate genotypic differences for dry matter production in both dry beans and snap beans grown under Al stress. However, these differences may be of little practical value under the field conditions normally encountered in the humid tropics where the amounts of soil Al cause large reductions in yields.